Passing an initialization list to a macro

Question

Why doesn\'t the commented out line in the following program compile?

#include 
#include 
using namespace std;

#define F1(a) 1

in         


        

Answer 1

A macro is not a function. It interprets your input vector{1,2,3} as 3 inputs, which are vector{1,2 and 3}. You can change this by making it an expression (vector{1,2,3}) (as you already did).

Everything in parantheses is an expression and vector(...) is a (*special member-)function so the preprocessor sees it as one expression.